Email accounts get locked for some reason every now and then, i don't know exactly what causes it.

Say, there exists an emailid for hosting account mydomain.com ( username : mydom, UID 32357 )as test@mydomain.com
All of a sudden , a file will be created as /home/mydom/mail/mydomain.com/test/inbox.lock with group ownership of 32357 ( same as UID for that hosting account )

This is what I could observe.
After that, neither the webmail nor email client would be able to access that email account.

Everything would be as it is. I mean the inbox file would exist.
My cpanel build is 8.5.4-RELEASE 72